Cardiac output derived from arterial pressure waveform analysis in patients undergoing liver transplantation: validity of a third-generation device

BACKGROUND: Hemodynamic monitoring is essential to a successful liver transplantation procedure. FloTrac, a hemodynamic monitor that uses arterial-waveform-based pulse contour analysis for cardiac output (CO) measurement, has proven useful in many clinical settings. One of the primary foci of FloTrac's recent third-generation software upgrade was improving its accuracy in low systemic vascular resistance status. We evaluated the accuracy of the upgraded FloTrac monitor during liver transplantation.

MATERIALS AND METHODS: Twenty-eight patients undergoing liver transplantation were enrolled in the study. Two sets of CO were measured with a radial arterial line connected to a FloTrac monitor (COFT) and a pulmonary artery catheter connected to a continuous cardiac output Vigilence monitor (COPAC). Simultaneous CO measurement was performed and recorded every 5 minutes throughout the surgery. Bland-Altman analysis was used to estimate the accuracy. The comparative method and reference method were considered interchangeable if the limits of agreement did not exceed a threshold set a priori at the greater of ±1 L/min, or a percentage error of lesser than 30%.

RESULTS: In all, 3234 paired data were collected. The bias was -0.8 L/min and the limits of agreements were -5.6 to 4.0 L/min. Percentage error was 75%. Regression analysis of the systemic vascular resistance index (SVRI) and the bias between COPAC and COFT showed that the bias was inversely related to the SVRI [r2=0.49; P<.001, y=-32.1983+9.9978 Log(x)].

CONCLUSIONS: Despite a software upgrade, the effectiveness of the FloTrac artery-derived cardiac output monitor for CO measurement during liver transplantation remains limited.